Method of making magnetic material



April 12, 1938.

Pig. 2.

c. HAASE ET AL 2,114,133

METHOD OF MAKING MAGNETIC MATERIAL Filed Nov. 22, 1934 Inventors: Carl Haase,

Otto Dahl,

Their- Attorney.

} Patented Apr. 12,1938

produc of the lines of force, but 0 of the material itself. A suitable method of obtaining the desired low instability in the material has been found to be a cold deformation after the last annealing. The most favorable ultimate degree of elongation, in this case, varies according to the choice of material. For the binary iron-nickel alloys the most favorable degree of elongation with regard to the lowest possible instability desired was found to be about 25%. With higher degrees of elongation, an increased However, the material behaves otherwise with regard to hysteresis. The hysteresis constant steadily decreases with an increasing degree of elongation, but since with the high degree of elongation, in the case of the binary iron-nickel alloys, the instability is increased, the favorable influence of high degrees of elongation on the hysteresis could not be utilized in the case of these alloys. hand, if a third constituent is alloyed with the iron-nickel alloy, such, for example, as aluminum, and particularly copper in suitable quantitles, the resulting alloy behaves difierently. A result can thereby be obtained whereby the inwhich' has attained its most favorable s with a 25-40% reducurrnon or MAKING Maems'rre Mar aret.

on November 22, 1934, Serial No. 754,302 lln Germany February M, 1934 hereinafter is designated as a preliminary degree of elongation in contradistinction to the subsequent degree of elongation which is' intended to represent the ultimate degree of elongation to which consideration was alone hither-. to given. The magnitude of this preliminary degree of elongation was regarded hitherto as unimportant, since it was thought that by a high degree of annealing and further considerable cold elongation the effect of the cold elongation preceding the annealing was entirely neutralized, in so far as work was not accomplished just within the range of the so-called critical degree of however, was generally In Goldschmidt et a1. Patent 1,801,150 a core is described which is used for magnetic purposes, especially such purposes where slight instability is important and where the required instability is ed, not by spatial subdivision of the path y a suitable treatment elongation which,

instability occurs.

/ of an example.

tered rom nickel and iron "car nickel and iron was employed. This alloy was worked up into strips of 0.06 mm. thickness. The preliminary degree of elongation amounted to 50% in tests set forth in column 1 of the following table, while in the tests set forth in column 2, it was greater than In both columns the values for the hysteresis constant h, quality factor On the other and instability s are in cent, existin tion. It is found that, 0 values in the tests carried out with a high preliminary degree of elongation, are substantially more favorable and the more so, the higher the preelongation, and that on the rties exhibit a low value in these alloy tlon in thickness, is not impaired again by a further increase in the degree of elongation but remains substantially constant, while the hysteresis decreases in the same way as in the binary alloys with an increasing degree of elongation. The Hminary degree of other hand, the individual prope fundamentally different behavior in dependence on the subsequent degree of elongation according to the preliminary degree of elongation chosen.

" l hysteresis constant a initial permeability In the following, the method according to the present invention is illustrated in detail by means As material, a binary alloy sinbonyl with 40% dicated, the latter in perg with equal final degrees of elonga-' n the one hand, all the which is characteristic forthe quality of a magnetic field, may be reduced in this case to values Column 2 not inconsiderably below-those obtained with compressed iron powder co The subject of the presen ed by means of which ternary-alloys and materials other than those mentioned above can be brought into a condition in which the hysteresis and the instability simultaneously or almost simultaneously reach their lowest values. This method takes into consideration not.only the. ude of the ultimate degree of elongation t invention is a meth Preliminary degree V 4 but also the magnitude of the degree of elonga- 90 percent tion which precedes the last annealing and which Whereaawith a preliminary degree of elongation of 50% corresponding to the previously discovered behavior of the binary iron-niclzel alnary degree of elongation, both properties, with the high preliminary degree of elongation, have a pronounced minimum which does not fully coincide with the minimum of instability, but which is nevertheless associated with a value of instability which canbe regarded for all cases occurring in practice as excellent and not requiring further improvement. It is, therefore, found that by a suitable choice of the preliminary degree of elongation and subsequent degree of elongation, if necessary, taking into account the most advantageous heat treatment between the two cold deformations, the course of the two most important magnetic properties, namely, the instability and the hysteresis, can be so influenced in dependence on the subsequent degree of elongation that a subsequent degree of elongation may be chosen whereby both properties may have substantially their optimum value.

The novel features which are characteristic of our invention are set forth with particularity in the appended claim. The invention itself, however, will be best understood from references to the following specification when considered in connection with the accompanying drawing, in which Fig. l is a reproduction of an X-ray defraction pattern of a 40-60% nickel-iron alloy which has been given a preliminary elongation of 50% and a subsequent elongation of 90%; while Fig. 2 is an X-ray defraction pattern of the same alloy which has been given a preliminary elongation of 98% and a subsequent elongation of 60%.

Figs. 1 and 2 of the drawlngillustrate the difference which exists with regard to the structure of material produced by the process according to the invention and a material produced by gamma the hitherto usual process. It is seen that in the material illustrated in Fig. 2, the atomic arrangement obtained is of a difierent character and is essentially more clearly marked than that lllustrated in Fig. 1. Thus by means of the high preliminary degree of elongation in conjunction with the temperature of the following heat treatment a predetermined recrystallization temperature is obtained which on its part, leads to a particularly well defined atomic arrangement in the last treatment. The conditions of tension and hardness produced by the cold elongation in the material, therefore, occur simultaneously with a position of the crystallites particularly favorable for magnetization. The use 01 the process according to the invention is, of course, not limited to binary ironnickel alloys but can also be used with other alloys such, for example, as the well-known ternary alloys or quaternary alloys, etc. or with alloys in the case of which equally favorable values hitherto could not be obtained. The method can also be used to obtain the most favorable magnetic properties obtainable in the case of alloys rich in iron, without the expensive nickel and thus render the cheap alloys applicable for many purposes for which hitherto more expensive alloys had to be used. The most favorable value of the preliminary degree of elongation and subsequent degree of elongation in this case varies, of course, according to the material chosen. It can, however, be experimentally determined in every case without difilculty. In the same way the influence of the most favorable method of heat treatment between the two cold deformations and any subsequent annealing treatment can readily be determined by experiment.

What we claim as new and desire to secure by Letters Patent of the United States, is:

The process of making a nickel-iron magnetic material containing about 40% nickel and about 60% iron which. comprises cold rolling the material to efi'ect an elongation of about 98%, annealing the material and completing said process by cold rolling the material to efiect an elongation of about 60%. 

